An eco-friendly car such as an electric car or a hybrid vehicle is mounted with a battery for supplying driving power of an electric motor, which is a driving source of a vehicle, and a battery management system (BMS) that monitors a state of the battery.
The eco-friendly car includes a main battery that supplies a driving voltage to a driving unit of the vehicle such as a motor, and an auxiliary battery which is charged during driving of the vehicle and supplies a voltage to electronic components of the vehicle at the time of starting the vehicle, or supplies a voltage required to operate a main relay of the main battery.
In the auxiliary battery, a current is intermitted by a relay. In the case in which an over-current flows in the relay according to a road of the vehicle when the auxiliary battery is charged, a phenomenon that the relay is fused may occur. As such, when the relay is fused, the auxiliary battery may be over-discharged. In this case, the auxiliary battery enters an over-discharged state, thereby causing the auxiliary battery to be damaged, or no longer available.